1337CSRI Real Time Clock (RTC) IC Equivalent & Substitute Parts

Part Overview

The 1337CSRI is a Real Time Clock (RTC) IC manufactured by Renesas Electronics Corporation, designed for clock/calendar applications with I2C interface. This component is classified as obsolete, making substitute parts necessary for new designs and ongoing production requirements. The 1337CSRI operates across a wide supply voltage range (1.8V to 5.5V) with battery backup capability (1.3V to 3.7V), supporting both 12-hour and 24-hour time formats with alarm and leap year functionality. Due to its obsolete status, equivalent alternatives from active manufacturers are required to maintain design continuity and ensure long-term component availability.

Key Parameters

Parameter	1337CSRI Specification
Manufacturer	Renesas Electronics Corporation
Category	Clock/Timing
Type	Clock/Calendar
Interface	I2C
Package / Case	16-SOIC (0.295", 7.50mm Width)
Voltage - Supply	1.8V ~ 5.5V
Voltage - Supply, Battery	1.3V ~ 3.7V
Current - Timekeeping (Max)	0.6µA @ 1.3V ~ 1.8V
Operating Temperature	-40°C ~ 85°C
Time Format	HH:MM:SS (12/24 hr)
Date Format	YY-MM-DD-dd
Features	Alarm, Leap Year, Square Wave Output
Mounting Type	Surface Mount
Product Status	Obsolete
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the 1337CSRI is determined by the following critical parameters:

Interface Compatibility: All substitute parts must support I2C (2-Wire Serial) interface to maintain firmware and hardware compatibility with existing designs.

Voltage Operating Range: Substitute parts must support the supply voltage range of 1.8V to 5.5V and battery backup voltage range of 1.3V to 3.7V. Parts with narrower voltage ranges may not function in all application scenarios.

Time and Date Format: All substitutes must support HH:MM:SS time format with both 12-hour and 24-hour modes, and YY-MM-DD-dd date format to ensure software compatibility.

Operating Temperature Range: Substitute parts must maintain operation across -40°C to 85°C to meet industrial and extended temperature requirements.

Core Features: Alarm functionality, leap year support, and square wave output are essential features that must be present in substitute parts.

Mounting Type: Surface mount technology is required for PCB integration compatibility.

Product Status: Active product status ensures long-term availability and ongoing manufacturer support.

Substitute parts are grouped into two categories: direct pin-compatible replacements in smaller packages (8-pin SOIC/TSSOP variants) and functionally equivalent alternatives with enhanced features (additional memory, improved power efficiency).

Parameter Comparison

Part Number	Manufacturer	Package	Interface	Voltage Supply	Battery Voltage	Time Format	Features	Operating Temp	Product Status
1337CSRI	Renesas Electronics	16-SOIC	I2C	1.8V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	Alarm, Leap Year, Square Wave	-40°C ~ 85°C	Obsolete
DS1338U-18+T&R	Analog Devices Inc./Maxim	8-TSSOP	I2C, 2-Wire Serial	1.71V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	Leap Year, NVSRAM, Square Wave	-40°C ~ 85°C	Active
DS1338Z-18+	Analog Devices Inc./Maxim	8-SOIC	I2C, 2-Wire Serial	1.71V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	Leap Year, NVSRAM, Square Wave	-40°C ~ 85°C	Active
DS1338Z-3+	Analog Devices Inc./Maxim	8-SOIC	I2C, 2-Wire Serial	2.7V ~ 5.5V	1.3V ~ 3.7V	HH:MM:SS (12/24 hr)	Leap Year, NVSRAM, Square Wave	-40°C ~ 85°C	Active
DS1308U-33+T	Analog Devices Inc./Maxim	8-TSSOP	I2C, 2-Wire Serial	3V ~ 5.5V	1.3V ~ 5.5V	HH:MM:SS (12/24 hr)	Leap Year, NVSRAM, Square Wave	-40°C ~ 85°C	Active
DS1340Z-33+T&R	Analog Devices Inc./Maxim	8-SOIC	I2C, 2-Wire Serial	2.97V ~ 5.5V	1.3V ~ 5.5V	HH:MM:SS (24 hr)	Leap Year, Trickle-Charger	-40°C ~ 85°C	Active
DS3232MZ+	Analog Devices Inc./Maxim	8-SOIC	I2C, 2-Wire Serial	2.3V ~ 4.5V	2.3V ~ 4.5V	HH:MM:SS (12/24 hr)	Alarm, Leap Year, Square Wave, SRAM	-40°C ~ 85°C	Active
DS3232MZ+TRL	Analog Devices Inc./Maxim	8-SOIC	I2C, 2-Wire Serial	2.3V ~ 4.5V	2.3V ~ 4.5V	HH:MM:SS (12/24 hr)	Alarm, Leap Year, Square Wave, SRAM	-40°C ~ 85°C	Active
DS1307+	Analog Devices Inc./Maxim	8-DIP	I2C, 2-Wire Serial	4.5V ~ 5.5V	2V ~ 4.6V	HH:MM:SS (12/24 hr)	Leap Year, NVSRAM, Square Wave	0°C ~ 70°C	Active
AB-RTCMC-32.768KHZ-AIGZ-S7-T	Abracon LLC	8-WCDFN	I2C, 2-Wire Serial	1V ~ 4.4V	Not specified	HH:MM:SS:hh (24 hr)	Alarm, Leap Year, Watchdog Timer	-40°C ~ 85°C	Active
M41T00SM6F	STMicroelectronics	8-SOIC	I2C, 2-Wire Serial	2.7V ~ 5.5V	2V ~ 4.6V	HH:MM:SS (24 hr)	Leap Year	-40°C ~ 85°C	Active

Engineering Selection Recommendations

Primary Substitutes (Highest Compatibility):

DS1338U-18+T&R and DS1338Z-18+ are the most direct functional equivalents to the 1337CSRI. Both parts maintain I2C interface compatibility, support the full voltage range (1.71V to 5.5V supply, 1.3V to 3.7V battery), preserve 12/24-hour time format capability, and include alarm, leap year, and square wave output features. These parts are manufactured by Analog Devices Inc./Maxim Integrated with active product status and RoHS3 compliance. The primary difference is package format: DS1338U-18+T&R uses 8-TSSOP while DS1338Z-18+ uses 8-SOIC. Both operate across the full -40°C to 85°C temperature range.

Secondary Substitutes (Extended Features):

DS3232MZ+ and DS3232MZ+TRL offer enhanced functionality with integrated SRAM (236B memory) and alarm capability. These parts maintain I2C interface and full temperature range operation but operate within a narrower voltage range (2.3V to 4.5V supply and battery). These substitutes are suitable for applications where the reduced voltage range is acceptable and additional memory is beneficial. Both variants are RoHS3 compliant with active product status.

Alternative Substitutes (Functional Equivalents with Constraints):

DS1340Z-33+T&R provides trickle-charger functionality and operates across -40°C to 85°C with I2C interface. However, this part supports only 24-hour time format (not 12-hour), which may require firmware modification. The voltage range (2.97V to 5.5V supply) is narrower than the original part.

M41T00SM6F from STMicroelectronics maintains I2C interface and full temperature range but supports only 24-hour time format and has a narrower battery voltage range (2V to 4.6V). This part is suitable only for applications that do not require 12-hour time format capability.

Not Recommended:

DS1307+ operates only at 4.5V to 5.5V supply voltage and 0°C to 70°C temperature range, making it unsuitable for the 1337CSRI's extended low-voltage and low-temperature requirements.

AB-RTCMC-32.768KHZ-AIGZ-S7-T does not specify battery voltage support, limiting its applicability for battery-backed RTC applications.

Frequently Asked Questions (FAQ)

Q: Can DS1338Z-18+ directly replace the 1337CSRI without PCB modification?

A: DS1338Z-18+ is functionally compatible but uses an 8-SOIC package versus the 1337CSRI's 16-SOIC package. PCB layout modification is required. Pin mapping must be verified against datasheets to ensure correct signal routing.

Q: What is the key difference between DS1338U-18+T&R and DS1338Z-18+?

A: Both parts are electrically identical with the same voltage range (1.71V to 5.5V), temperature range (-40°C to 85°C), and feature set. The difference is packaging: DS1338U-18+T&R uses 8-TSSOP (0.118" width) while DS1338Z-18+ uses 8-SOIC (0.154" width). Selection depends on PCB footprint requirements.

Q: Why is DS1307+ not recommended as a substitute?

A: DS1307+ operates only at 4.5V to 5.5V supply voltage, which does not meet the 1337CSRI's 1.8V minimum requirement. Additionally, its operating temperature range (0°C to 70°C) does not extend to the -40°C lower limit. This part is unsuitable for applications requiring extended voltage and temperature ranges.

Q: Does DS3232MZ+ support the full voltage range of the 1337CSRI?

A: No. DS3232MZ+ operates at 2.3V to 4.5V for both supply and battery voltage, which is narrower than the 1337CSRI's 1.8V to 5.5V supply range and 1.3V to 3.7V battery range. This part is suitable only for applications operating within its specified voltage window.

Q: Are all substitute parts RoHS3 compliant?

A: All recommended substitute parts (DS1338 series, DS3232 series, M41T00SM6F) are RoHS3 compliant. The AB-RTCMC part is REACH unaffected. Compliance documentation should be verified with the specific manufacturer for your procurement requirements.

Q: What is the significance of the 56B memory in DS1338 variants?

A: The 56-byte NVSRAM (Non-Volatile Static RAM) in DS1338 variants provides additional storage for user data that persists during power loss. The 1337CSRI does not specify memory size, so this feature represents an enhancement in substitute parts.

Q: Can I use M41T00SM6F if my application only requires 24-hour time format?

A: Yes, M41T00SM6F is compatible if your application does not require 12-hour time format support. However, verify that the battery voltage range (2V to 4.6V) meets your backup power requirements, as it is narrower than the 1337CSRI's 1.3V to 3.7V range.

Q: What packaging options are available for I2C RTC substitutes?

A: Available packages include 8-SOIC (0.154" width), 8-TSSOP (0.118" width), 8-WCDFN, and 8-DIP (through-hole). Surface mount options (SOIC, TSSOP, WCDFN) are preferred for modern PCB designs. Through-hole options (DIP) are available but less common in current production.

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